Mineral wool product

ABSTRACT

A mineral wool batt for use as a plant growth medium, particularly in applications for growing vegetation (including plants) in which water retention and/or the avoidance of water run-off is of interest. The mineral wool batt has an absorbent layer which comprises needled mineral wool fibers; superabsorbent particles in the absorbent layer may be sandwiched between a denser upper and/or lower barrier layer(s) which assist in preventing their escape.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national counterpart application ofInternational Application Serial No. PCT/EP2012/060311, filed May 31,2012, under 35 U.S.C. §371, which claims priority to EuropeanApplication Serial No. 11168311.6, filed May 31, 2011, the entiredisclosures of each of which are hereby incorporated by referenceherein.

TECHNICAL FIELD

The present invention relates to a mineral wool product for use inhorticultural, landscaping, green roof or urban gardening applications,more particularly for growing vegetation (including plants) in whichwater retention and/or the avoidance of water run-off is of interest.

BACKGROUND

The use of mineral fibre products for cultivating plants is disclosed,for example, in EP0280338A1 which describes the incorporation of higherdensity flakes of mineral fibres (which have greater water retainingcapacity) in a matrix of its mineral fibre mat. WO 91/08662 discloses aplant growing medium comprising mineral fibres which incorporateslignite as an agent for increasing the water retention ability;traditionally used manufacturing agents and aids such as binding agents,tensides, superabsorbents, and agents for controlling the air contentand the water retention properties of the growing medium, such asexpanded clay, foam plastic compounds, vermiculite, perlite,cellulose-containing compounds and top soil may also be incorporated.

Despite these and other proposals, a need still exists for a moreadvantageous form of mineral wool product for the applicationsenvisaged.

SUMMARY

According to one of its aspects, the present invention provides amineral wool product as defined in claim 1. Other aspects of theinvention are defined in other independent claims. Dependent claimsdefine preferred and/or alternative aspects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-section of one embodiment of a mineral wool batt;

FIG. 2 shows a cross-section of another embodiment of a mineral woolbatt; and

FIGS. 3-7 show schematic representations of stages in preferredmanufacturing techniques for the batt of FIG. 2.

DETAILED DESCRIPTION

In accordance with one of its aspects, the present invention provides amineral wool batt comprising an absorbent layer comprising mineral woolfibres, characterised in that the absorbent layer comprises needledmineral wool fibres and superabsorbent particles.

The mineral fibres are preferably stone wool; they may be glass wool.They may be crimped; they may have an average diameter between 2 and 9microns.

Physical integrity of the batt and retention of the superabsorbentparticles in the batt are preferably provided by intertwining of themineral wool fibres, for example by needling; this avoids the necessityof using a heat curable binder which, in turn, avoids the need ofpassing the mineral wool batt through a curing oven (typically operatedat a temperature of about 200° C.) which could degrade or even destroythe superabsorbent particles. Furthermore, avoiding the use ofconstituents of some binder systems, notably constituents of phenolformaldehyde based binder systems, which may be deleterious to plantgrowth, provides an additional advantage.

Whilst the mineral wool batt is preferably substantially devoid ofbinder, a small amount of binder may be present, for example in aquantity of less than 1% by weight, preferably less than 0.5% or lessthan 0.3% by weight. Binder may be present if, for example, the mineralwool batt incorporates recycled mineral wool fibres that were originallymanufactured using a binder. Nevertheless, the mineral wool batt ispreferably manufactured without applying binder to any freshly formedfibres.

During needling or intertwining of the mineral wool fibres, needlingaids, for example oils or lubricants, may be used.

The structure of needled fibres is particularly favourable to initialand/or cycled water retention and/or initial and/or cycled waterretention content and/or VSE water content and/or WOK water content, inparticular when combined with the presence of superabsorbent particlesand/or a reduction in the amount of binder for the fibres (andpreferably the elimination of the presence of a binder for the fibres).

The nominal thickness of the mineral wool batt may be ≧10 mm or ≧15 mmor ≧40 mm or ≧50 mm; it may be ≦140 mm or ≦120 mm. The nominal thicknessof the absorbent layer or core may be ≧8 mm or ≧10 mm or ≧30 mm or ≧40mm and/or ≦130 mm or ≦110 mm. Where upper and/or lower barrier layersare provided, these may have a nominal thickness which is ≧3 mm or ≧5 mmand/or ≦15 mm or ≦12 mm.

The average density of the mineral wool batt may be ≧20 kg/m³,preferably ≧40 kg/m³; it may be ≦200 kg/m³.

The density of the absorbent layer or core of the mineral wool batt maybe ≧20 kg/m³, preferably ≧30 kg/m³; it may be ≦190 kg/m³, preferably≦150 kg/m³. The density of the upper and/or lower barrier layers of themineral wool batt may be ≧25 kg/m³, preferably ≧50 kg/m³; it may be ≦200kg/m³, preferably ≦150 kg/m³.

The density of the upper and/or lower barrier layers when provided maybe greater than the density of the absorbent layer or core by at least 5kg/m³, preferably by at least 10 kg/m³, more preferably by at least 15kg/m³.

The superabsorbent particles may comprise superabsorbent polymerparticles; they may be adapted to absorb at least 100 times or at least200 times their own weigh of distilled water, preferably at least 400times their own weight of distilled water.

The superabsorbent polymer particles may be selected from the groupconsisting of: poly-acrylic acid sodium salts; polyacrylamidecopolymers, copolymers of acrylamide and sodium acrylate, ethylenemaleic anhydride copolymers, cross-linked carboxymethyl celluloses,polyvinyl alcohol copolymers, cross-linked polyethylene oxides, andstarch grafted copolymer of polyacrylonitrile.

The mineral wool batt is preferably devoid or substantially devoid of:

-   -   carbonaceous materials other than the superabsorbent particles,        for example, lignite which would increase its water retention        ability; and/or    -   cellulose fibres.

The particle size of the superabsorbent particles is preferably selectedsuch that:

-   -   90%, and more preferably 95% of the particles (by weight and/or        by number) have a diameter of less than 1 mm and/or    -   The average particle size (by weight and/or by number) is within        the range of 0.4-0.8 mm, and preferably within the range 0.5-0.7        mm and/or    -   80% of the particles (by weight and/or by number) have a        diameter within the range of 0.4-2.1 mm, and preferably within        the range 0.5-2.0 mm and/or    -   20% of the particles (by weight and/or by number) have a        diameter within the range of 0.05-0.5 mm.

The particle size distribution may be determined by a sieve analysis(also known as a graduation test); a typical procedure for such ananalysis comprises passing a representative sample of particles througha series of sieves in a nested stack, each successive sieve in thenested stack having a wire screen with openings that are smaller thanthe openings of the previous sieve in the stack and weighing theparticles retained by each sieve after mechanical shaking.

The mineral wool batt may comprise at least 10 g/m² of superabsorbentparticles (dry weight of superabsorbent particle per surface area ofmineral wool batt) and preferably at least 50 g/m² or at least 75 g/m²;it may comprise not more than 250 g/m² or not more than that 200 g/m² ornot more than 150 g/m² of superabsorbent particles.

The mineral wool batt may also comprise one or more fertilisers and/orpesticides and/or herbicides and/or growing aids and/or seeds. Themineral wool batt of the invention is particularly suitable for use inone or more of the following applications:

-   -   Particularly in arid climates, growing vegetation or crops or        growing grass for sports facilities, particularly golf courses.        The mineral wool batts may be covered with a surface layer of        soil or sand. The mineral wool batts may be installed at their        desired site prior to seeding or planting of plants or        vegetation. Alternatively, the mineral wool batts may be used as        a support for the initial growing of plants or vegetation under        controlled or favourable conditions prior to transfer of the        mineral wool batts incorporating pre-grow vegetation to their        desired site.    -   Particularly on slopes and inclines, for example at the upper        portions of landscaped slopes or slopes along motorways or        transport cuttings, for preventing run-off of rainwater from the        elevated portions and thus favouring retention of vegetation at        the upper portions of such slopes or inclines.    -   For use in pots, for example for growing pot plants.    -   For use as part of green roof systems as a growing medium.    -   For use in herb and/or other crop cultivation.    -   For use in urban gardening applications.

According to another aspect, the invention provides a method of growingvegetation in which the vegetation is grown on a growth mediumcomprising a mineral fibre batt comprising needled mineral wool fibres.At least one surface of the mineral fibre batt may be exposed so thatthe vegetation is grown from an exposed surface directly from themineral fibre batt. Alternatively, the mineral wool batt may bepartially, substantially of completely covered, for example be sand,soil or another growing medium, such that the vegetation is grownthrough a growing medium covering the mineral wool batt.

Non-limiting examples of the invention are described below withreference to:

FIG. 1 which is a cross-section of one embodiment of a mineral woolbatt;

FIG. 2 which is a cross-section of another embodiment of a mineral woolbatt; and

FIGS. 3 to 7 which are schematic representations of stages in preferredmanufacturing techniques for the batt of FIG. 2.

The mineral wool batt 10 shown in FIG. 1 comprises an absorbent layer 11comprising superabsorbent particles 12 held between fibres of needledmineral wool. In this embodiment, the superabsorbent particles 12 aredistributed substantially evenly over the thickness of the mineral woolbatt.

The mineral wool batt 10 shown in FIG. 2 comprises an absorbent layer inthe form of a core 11 comprising super absorbent particles 12 sandwichedbetween an upper barrier layer 13 and a lower barrier layer 14. Thesuperabsorbent particles 12 are retained between the interstices of thefibres of the absorbent layer or core 11 (as in FIG. 1) and alsoprevented from escaping from the major surface of the batt by the upper13 and lower 14 barrier layers of mineral wool which have a densitygreater than that of the core.

The mineral wool batt 10 may be manufactured using the following steps:

In an initial step, represented in FIG. 3, a semi-finished mineral woolbatt 21 is provided by assembling mineral wool fibres in to a blanket.The semi-finished mat may be provided by folding layers of mineral woolfibres using a reciprocating motion of a pendulum 22 so that fibres areevenly distributed in several layers and subsequently compressing thisblanket to an initially desired density, for example in the range of 40to 140 kg/m³. The semi-finished batt 21 is free of binder, no binderhaving been applied to the fibres or to the blanket.

In a subsequent step, represented in FIG. 4, a desired quantity ofsuperabsorbent particles 12 is distributed at an upper surface of thesemi-finished mineral wool batt 21 via a nozzle 32 as the batt 21advances along a production line. Preferably, the superabsorbentparticles are distributed substantially evenly over substantially theentire upper surface of the batt 21; a border strip of, for example,about 5-15 mm along each side edge of the upper surface of the batt 21may nevertheless remain substantially free of superabsorbent particlesso as to avoid spillage of the superabsorbent particles during theirapplicant and/or during subsequent operations.

Once the superabsorbent particles have been distributed at the uppersurface of the batt 21, a moving covering belt (not shown) is applied tocover the upper surface and the superabsorbent particles and travelswith the batt to the next step in the production process so at tominimise fall off of the superabsorbent particles from the batt 21. Thecovering belt may press some of the superabsorbent particles in to anupper surface of the batt 21.

The semi-finished batt 21 then travels to a needling station representedin FIG. 5 at which, just after separation of the covering belt (notshown) from the upper surface of the semi-finished mineral wool batt 21,a series of upper surface needles 43 are reciprocated up and downthrough the upper surface of the semi-finished mineral wool batt 21. Atthe same time, a series of lower surface needles 44 are reciprocated upand down through the lower surface of the semi-finished mineral woolbatt 21. The effects of the needling action are:

-   -   To push the superabsorbent particles 12 in to the core 11 of the        mineral wool batt and to needle the fibres between each other        (which increases the stability of the mineral wool batt);    -   To increase the density of the core 11 of the mineral wool batt        21, preferably to a density in the range 30 to 120 kg/m³ or in        the range 30 to 160 kg/m³;    -   To cause the super absorbent particles 12 to be trapped between        fibres at the core 11 of the mineral wool batt;    -   To create an upper barrier layer 13 and a lower barrier layer        14, each of which is has a higher density than the core 11 of        the batt and each of which provides increased resistance to        escape of superabsorbent particles 12 from the batt 21.

The density of the upper barrier layer 13 and a lower barrier layer 14may be in the range 50 to 140 kg/m³ or in the range 50 to 180 kg/m³.

The needling operation may be conducted in a number of sub-steps. Forexample:

-   -   A first sub-step in which (a) the upper surface needles are used        with long strokes to push the superabsorbent particles in to the        core or the batt 21 and (b) the lower surface needles 44 are        used with short strokes to create the higher density needled        lower barriers lay 14; and    -   A second sub-step in which, once the superabsorbent particles        have been pushed towards the core 11 of the batt 21, the upper        surface needles 43 are used with short strokes to create the        higher density needled upper barriers lay 13.

The mineral wool batt comprising superabsorbent particles may then befurther processed and/or packaged (preferably under compression) in torolls or blocks or even cut in to flocks ready for transportation anduse.

In the FIGS. 4 and 5 arrangement, a pendulum 22 (or equivalentarrangement) is used to superimpose initial layers of fibres, forexample by folding, to form a semi-finished mineral wool batt 21 and thesuperabsorbent particles are initially distributed at an upper surfaceof this assembled semi-finished mineral wool batt 21. Alternatively, oradditionally, superabsorbent particles may be distributed on an initiallayer of fibres, for example before a pendulum, prior to portions of theinitial layer of fibres being superimposed upon each other to form anassembled semi-finished mineral wool batt. In this way, as illustratedin FIG. 6, superabsorbent particles 12′ are positioned at or in thevicinity of the core 11 of the semi-finished mineral wool batt 21 beforeneedling (due to prior super positioning of the layers from which thesemi-finished mineral wool batt is assembled) and the needling thenserves:

-   -   If required, to push any superabsorbent particles 12 which are        distributed at a surface of the semi-finished mineral wool batt        21 in to the absorbent later or core 11 of the mineral wool        batt; and/or    -   To more evenly distribute superabsorbent particles 12′ which are        already positioned at or in the vicinity of the absorbent layer        or core 11; and/or    -   to needle the fibres between each other (which increases the        stability of the mineral wool batt); and/or    -   To increase the density of the absorbent later or core 11 of the        mineral wool batt 21, preferably to a density in the range 30 to        120 kg/m³ or in the range 30 to 160 kg/m³; and/or    -   To cause the super absorbent particles 12 to be trapped between        fibres at the absorbent layer or core 11 of the mineral wool        batt; and/or    -   To create an upper barrier layer 13 and a lower barrier layer        14, each of which is has a higher density than the core 11 of        the batt and each of which provides increased resistance to        escape of superabsorbent particles 12 from the batt 21.

Such an approach may be used when the semi-finished mineral wool batt 21is assembled by superimposing two or more initial layers of fibres, forexample by pendulum folding.

FIG. 7 is similar to FIG. 6 and illustrates: (i) on its left hand sidethe substantially horizontal orientation of fibres and the arrangementof superabsorbent particles in layer(s) prior to needling and (ii) onits right hand side, the effect of needling creating a more evendistribution of superabsorbent particles throughout the thickness of themineral wool batt, or at least the core of the mineral wool batt, and anorientation of fibres of the needled mineral wool batt with asignificant proportion of the fibres having a vertical or non-horizontalcomponent of direction and the mass of fibres forming interstices inwhich at least some of the super absorbent particles are trapped.

EXAMPLES

The following samples were tested:

Examples batts of needled, stone wool fibres with no binder cut in to a¼ 1.1 and 1.2 circle with a radius of 19.5 cm. Density: 110 kg/cm³;thickness: 20 mm; quantity of superabsorbent particles: 60 g/m² Examplesbatts of needled, stone wool fibres with no binder cut in to a ¼ 2.1 and2.2 circle with a radius of 19.5 cm. Density: 110 kg/cm³; thickness: 20mm; no superabsorbent particles Example 3 batts of needled, stone woolfibres with no binder cut in to a 17 cm square. Density: 110 kg/cm³;thickness: 20 mm; quantity of superabsorbent particles: 15 g/m² Example4 batts of needled, stone wool fibres with no binder cut in to a 17 cmsquare. Density: 110 kg/cm³; thickness: 20 mm; no superabsorbentparticles Examples As examples 1.1 and 1.2 but cut to size to fit testapparatus 5.1 and 5.2 Examples As example 3 but cut to size to fit testapparatus 6.1 and 6.2 Examples As examples 2.1, 2.2 and 4 but cut tosize to fit test apparatus 7.1 and 7.2Initial Water Retention and Initial Water Content (Cycle 1-C1)

Three samples of each example were tested; the results presented beloware the mean average of the three samples.

At the beginning of each test for initial water retention, each sampleis weighed, its dry weight recorded, and then soaked in tap water forabout 2 hours; the samples are then placed on a metal grid at normalroom conditions (temperature about 20° C.±5° C.; pressure about 101kPa±20%; relative humidity about 40% to 80%, preferably about 60%±10%)in the laboratory for conditioning. The samples are weighted after 5minutes 1 day, 2 days, 3 days and 4 days.

Table 1 shows the water retention which is calculated as(mass of wet sample−mass of dry sample)/mass of dry sampleand expressed as kg water per kg (dry weight) of mineral wool batt. Thet0 initial water retention is defined as the water retention after fiveminutes (i.e. once the excess water from the sample being soaked isallowed to drain off).

TABLE 1 water retention (kg/kg) 5 min Example (t0) 1 day 2 day 3 day 4day 1.1 10.4 — — 4.6 2.7 1.2 10.4 8.1 5.9 3.5 1.4 2.1 7.3 — — 2.1 0.12.2 8.7 6.5 4.3 2.0 0.1

Table 2 shows the water content which is calculated as(mass of wet sample−mass of dry sample)/mass of wet sampleand expressed as a percentage. The initial water content is defined asthe water content after five minutes (i.e. once the excess water fromthe sample being soaked is allowed to drain off).

TABLE 2 water content (%) 5 min Example (t0) 1 day 2 day 3 day 4 day 1.191 — — 82 73 1.2 91 89 85 78 56 2.1 88 — — 68 11 2.2 90 87 81 67 7Cycled Water Retention and Cycled Water Content (Cycles 1 to 5-C1 to C5)

Cycled water retention and cycled water content of Examples 3 and 4 wasevaluated in a similar way as above and defined as:

Cycle 1 C1 Determined in the same way as initial water retention andinitial water content Cycle 2 C2 Determined in respect of samples which,after cycle 1 are dried, soaked again in tap water for at least 2 hoursand re-measured Cycle 3 C3 Determined in respect of samples which, aftercycle 2 are dried, soaked again in tap water for at least 2 hours andre-measured Cycle 4 C4 Determined in respect of samples which, aftercycle 3 are dried, soaked again in tap water for at least 2 hours andre-measured Cycle 5 C5 Determined in respect of samples which, aftercycle 4 are dried, soaked again in tap water for at least 2 hours andre-measuredand in which the drying out of the samples between each cycle is carriedout by allowing the samples to dry in the normal room conditions untiltheir water retention is less than 0.1, preferably substantially 0. Theresults are shown in Tables 3, 4, 5 and 6. Three samples of each examplewere tested; the results presented below are the mean average of thethree samples.

TABLE 3 Example 3-water retention (kg/kg) following each cycle 5 minCycle (t0) 1 day 2 day 3 day 4 day C1 9.8 7.4 5.2 3.1 1.1 C2 8.9 6.9 5.13.6 1.8 C3 8.4 6.8 5.1 3.2 1.9 C4 8.3 6.0 4.3 2.2 0.8 C5 8.1 6.2 4.7 3.42.4

TABLE 4 Example 3-water content (%) following each cycle 5 min Cycle(t0) 1 day 2 day 3 day 4 day C1 90 87 84 78 65 C2 89 87 84 76 65 C3 8986 81 69 44 C4 89 86 82 77 71 C5 89 86 82 75 58

TABLE 5 Example 4-water retention (kg/kg) following each cycle 5 minCycle (t0) 1 day 2 day 3 day 4 day C1 8.6 6.5 4.7 2.7 0.9 C2 8.0 6.0 4.12.5 1.1 C3 7.8 6.1 4.4 2.5 1.1 C4 7.4 5.3 3.4 1.3 0.2 C5 7.4 5.7 4.0 2.71.6

TABLE 6 Example 4-water content (%) following each cycle 5 min Cycle(t0) 1 day 2 day 3 day 4 day C1 90 87 82 72 39 C2 89 86 80 72 52 C3 8986 81 71 52 C4 88 84 77 53 13 C5 88 85 80 73 61VSE Water Content (Vacuum Simulated Evaporation)

A vacuum simulated evaporation (VSE) test is performed using a sandsuction table according to European standard EN 13041 of December 1999.The sample is cut to the internal dimensions of a rigid test ring(internal diameter 100 mm, height 50 mm, open at both ends and of knownmass), weighed (dry weight), placed in the test ring and soaked in wateruntil saturation. The test ring is then placed on the sand suction tableand left for 24 hours to reach equilibrium conditions before beingweighed so as to determine the water content of the sample. The testring is then returned to the sand suction table, a vacuum of −3.2 cmwater is applied through the base of the sand suction table and thesample is left in these conditions for 24 hours to reach equilibriumbefore being weighed again to determine the water content of the sample.The test ring is then returned to the sand suction table, a vacuum of−10 cm water is applied through the base of the sand suction table andthe sample is left in these conditions for 24 hours to reach equilibriumbefore being weighed again to determine the water content of the sample.The procedure is repeated systematically so as the determine the watercontent of the sample after equilibrium after sequential application ofa vacuum of −3.2 cm water, −10 cm water, −32 cm water, −50 cm water and−100 cm water, the results being shown in Table 7:

TABLE 7 VSE water content (%) After −3.2 −10 −32 −50 −100 vacuum of: cmcm cm cm cm Example 5.1 96 91 56 50 48 Example 6.1 96 90 46 38 37Example 7.1 96 94 20 9 6WOK Water Absorption

The WOK method (WOK=water uptake characteristic) as developed byStichting RHP, Galgeweg 38, 2691 MG's-Gravenzande, The Netherlandswww.rhp.nl is used to determine water re-absorption of examples 5.2, 6.2and 7.2. The sample to be tested is placed in a ring, soaked in wateruntil saturation, left to reach equilibrium on a sand suction table,weighed to determine its initial water content, dried to equilibrium ona sand suction table at a vacuum of −100 cm water and then further driedin an oven at 40° C. for 72 hours before being weighed (dry weight). Thesample is arranged such that the mineral fibres are just in contact withwater and its water content is determined as a function of time andexpressed as a % of initial water content. Results are shown in Table 8:

TABLE 8 WOK water content (%) Time (minutes) 15 30 60 90 120 240 Example5.2 52 64 74 78 80 85 Example 6.2 83 89 92 93 94 95 Example 7.2 72 72 7272 72 72

Preferred individual characteristics and combinations of characteristicsof products in accordance with the invention are set out in thefollowing tables:

Preferred Characteristics for Initial Water Retention (kg/kg):

More Most Characteristic Preferred preferred preferred tO initial waterretention ≧6.5 ≧7 ≧8.5 initial water retention after day 1 ≧5.5 ≧6.5 ≧7initial water retention after day 2 ≧4.0 ≧4.5 ≧5 initial water retentionafter day 3 ≧2 ≧3 ≧4 initial water retention after day 4 ≧0.8 ≧1.0 ≧2Preferred Characteristics for Initial Water Content (%):

More Most Characteristic Preferred preferred preferred tO initial watercontent ≧70 ≧80 ≧85 initial water content after day 1 ≧65 ≧75 ≧82initial water content after day 2 ≧60 ≧70 ≧80 initial water contentafter day 3 ≧50 ≧65 ≧70 initial water content after day 4 ≧5 ≧50 ≧55Preferred Characteristics for Cycled Water Retention After Cycle 4(kg/kg)

More Most Characteristic Preferred preferred preferred t0 cycled waterretention ≧6.5 ≧7.0 ≧7.5 cycled water retention after day 1 ≧4.5 ≧5.0≧5.5 cycled water retention after day 2 ≧2.5 ≧3.0 ≧4.0 cycled waterretention after day 3 ≧0.8 ≧1.0 ≧1.5 cycled water retention after day 4≧0.1 ≧0.2 ≧0.5Preferred Characteristics for Cycled Water Content After Cycle 4(%)

More Most Characteristic Preferred preferred preferred t0 cycled watercontent ≧75 ≧80 ≧85 cycled water content after day 1 ≧72 ≧77 ≧82 cycledwater content after day 2 ≧70 ≧75 ≧80 cycled water content after day 3≧50 ≧60 ≧70 cycled water content after day 4 ≧10 ≧50 ≧65Preferred Characteristics for VSE Water Content (%)

More Most Characteristic Preferred preferred preferred VSE water contentafter vacuum ≧85 ≧90 ≧92 of −3.2 cm VSE water content after vacuum ≧70≧80 ≧85 of −10 cm VSE water content after vacuum ≧35 ≧40 ≧50 of −32 cmVSE water content after vacuum ≧20 ≧30 ≧40 of −50 cm VSE water contentafter vacuum ≧15 ≧30 ≧40 of −100 cmPreferred Characteristics for WOK Water Content (%)

More Most Characteristic Preferred preferred preferred WOK water contentafter 15 minutes ≧50 ≧65 ≧75 WOK water content after 30 minutes ≧65 ≧75≧80

The invention claimed is:
 1. A mineral wool batt having an averagedensity of at least 20 kg/m³, comprising an absorbent core layersubstantially free of binder comprising needled mineral wool fibres andsuperabsorbent particles; and a first mineral wool barrier layeradjacent to the core layer, the first mineral wool barrier layer havinga density greater than the density of the core layer.
 2. The mineralwool batt of claim 1 wherein the absorbent core layer is positionedbetween the first mineral wool barrier layer and a second mineral woolbarrier layer adjacent to the core layer having a density greater thanthe density of the core layer, where each of the first and/or secondbarrier layers prevents substantial escape or contributes to preventingescape of the superabsorbent particles from the absorbent core layer. 3.The mineral wool batt of claim 2, wherein the first and/or secondmineral wool barrier layer(s) comprises needled mineral woolsubstantially free of binder.
 4. The mineral wool batt of claim 1,wherein the mineral wool batt comprises a quantity of superabsorbentparticles in the range of 10 g/m² to 250 g/m².
 5. The mineral wool battof claim 1, wherein the mineral wool batt has at least one of or anycombination of the following characteristics: A t0 initial waterretention of at least 6.5 times its own weight and/or A t0 initial watercontent of at least 70% and/or A cycle 4, cycled water retention after 2days of at least 2.5 times its own weight and/or A cycle 4, cycled waterretention after 2 days of at least 75% and/or A VSE water content aftervacuum of −10 cm of at least 70% and/or A WOK water content after 30minutes of at least 65%.
 6. A method of manufacturing a mineral woolbatt having an average density of at least 20 kg/m³, comprising thesteps of: providing a semi-finished mineral wool batt substantially freeof binder; distributing super absorbent particles on a surface of thesemi-finished mineral wool batt so that the superabsorbent particles aresupported at the surface of the semi-finished mineral wool batt and/orproviding superabsorbent particles within the semi-finished mineral woolbatt; needling the semi-finished mineral wool batt so at to push anysuperabsorbent particles supported at the surface towards a core of thesemi-finished mineral wool batt and/or increase the distribution withinthe core of the semi-finished mineral wool batt of any superabsorbentparticles initially provided within the semi-finished mineral wool batt;and providing by needling a first mineral wool barrier layer adjacent tothe core layer having a density which is greater than the density of thecore of the semi-finished mineral wool batt.
 7. The method of claim 6,further comprising the step of providing by needling a second mineralwool barrier layer adjacent to the core and having a density which isgreater than the density of the core of the semi-finished mineral woolbatt so that the core is positioned between the first and second mineralwool barrier layers.
 8. The method of claim 7, wherein the needlingcomprises simultaneously needling upper and lower surfaces of themineral wool batt to form the first and second barrier layer(s).
 9. Themethod of claim 6, further comprising the step of packaging the mineralwool batt incorporating the superabsorbent particles in its core in acompressed configuration.
 10. The method of claim 9, wherein between thestep of the semi-finished mineral wool batt being provided and the stepof the mineral wool batt being packaged, the temperature of the core ofthe mineral wool batt is not raised above 120° C.
 11. A method ofretaining water for the growth of vegetation, comprising using themineral wool batt of claim 1 as a water retention medium in the growthof vegetation.
 12. The method of claim 11, wherein the mineral wool batthas at least one of or any combination of the following characteristics:A t0 initial water retention of at least 6.5 times its own weight and/orA t0 initial water content of at least 70% and/or A cycled 4 cycledwater retention after 2 days of at least 2.5 times its own weight and/orA cycled 4 cycled water retention after 2 days of at least 75% and/orVSE water content after vacuum of −10 cm of at least 70% and/or A WOKwater content after 30 minutes of at least 65%.
 13. The method of claim11, wherein the mineral wool batt comprises an absorbent layercomprising mineral wool fibres, wherein the absorbent layer comprisesneedled mineral wool fibres and superabsorbent particles.
 14. The methodof claim 11, wherein the mineral wool batt is manufactured by a methodcomprising the steps of: providing a semi-finished mineral wool battsubstantially free of binder; distributing super absorbent particles ona surface of the semi-finished mineral wool batt so that thesuperabsorbent particles are supported at the surface of thesemi-finished mineral wool batt and/or providing superabsorbentparticles within the semi-finished mineral wool batt; and needling thesemi-finished mineral wool batt so at to push any superabsorbentparticles supported at the surface towards a core of the semi-finishedmineral wool batt and/or increase the distribution within the core ofthe semi-finished mineral wool batt of any superabsorbent particlesinitially provided within the semi-finished mineral wool batt.
 15. Themineral wool batt of claim 4, wherein the mineral wool batt comprises aquantity of superabsorbent particles in the range of 50 g/m² to 200g/m².